Packaging machine

ABSTRACT

A packaging machine, includes a pair of sealing jaws that sandwiches and seals a sealed portion of a tubular film. The packaging machine is provided with a first rotating shaft for supporting one sealing jaw, a second rotating shaft for supporting the other sealing jaw, a rotary encoder, and an entrapment determination part. When the first rotating shaft and the second rotating shaft approach or move away, the rotary encoder measures the movement amount of the first rotating shaft in relation to the second rotating shaft in an approaching direction or a moving away direction. The entrapment determination part determines whether or not articles are present in the sealed portion based on the movement amount.

TECHNICAL FIELD

The present invention relates to a packaging machine, and particularlyrelates to a packaging machine in which a pair of sealing memberssandwiches and seals portions of a film.

BACKGROUND ART

In the past, there have been packaging machines with sealing means whichuse sealing members to sandwich and seal a packaging material. Forexample, Patent Literature 1 (Japanese Laid-open Patent Application No.2007-302261) and Patent Literature 2 (Japanese Laid-open PatentApplication No. H3-69428) disclose a packaging machine which usessealing members driven by a servo motor to sandwich and heat-seal apackaging material shaped into a tubular shape, and thereby packagesgoods to be packaged.

With this type of packaging machine, when the packaging material issandwiched and sealed by the sealing members, sometimes the goods to bepackaged or the like get trapped in the sealed portions and the packageis thereby incompletely sealed.

Patent Literature 1 (Japanese Laid-open Patent Application No.2007-302261) discloses the feature that the drive current of the servomotor, or in other words, the torque of the servo motor, is measured,and when the drive current exceeds a predetermined value, the sealedportions are determined to have trapped a foreign object and a poor sealis detected. Patent Literature 2 (Japanese Laid-open Patent ApplicationNo. H3-69428) discloses the feature that the rotational angle of theservo motor is measured, and presence of objects in the sealed portionsare detected based on a delay from the target position of the rotationalposition.

SUMMARY OF THE INVENTION Technical Problem

In some packaging machines, a separate mechanism is used instead of aservo motor as the drive source for sandwiching the packaging materialbetween the sealing members. For example, there are cases in which themechanism used as the drive source cannot perceive the force/momentexerted on the packaging material by the drive source and positionalinformation pertaining to the drive source (e.g., the rotational angleof the motor, etc.), directly from information obtained from the drivesource. In such cases, it is not possible to detect the presence ofarticles trapped in the sealed portions based on the informationobtained from the drive source.

One object of the present invention is to provide a packaging machinewhich uses sealing members to sandwich and seal a packaging material,wherein the presence of articles trapped in the sealed portions can bedetected even when the mechanism used as the drive source of the sealingmembers is incapable of causing the force/moment exerted on thepackaging material by the drive source and positional informationpertaining to the drive source, to be directly perceived frominformation obtained from the drive source.

Solution to Problem

In a packaging machine according to the present invention, a pair ofsealing members is configured to sandwich and seal a sealed portion of afilm. The packaging machine is provided with a first support partconfigured to support one of the sealing members and a second supportpart configured to support the other of the sealing members, a movementamount detector, and an entrapment determination part. The movementamount detector is configured to measure the relative movement amount ofthe first support part in relation to the second support part in anapproaching direction or a moving away direction, when the first supportpart and the second support part approach or move away. The entrapmentdetermination part is configured to determine whether or not articlesare present in the sealed portion based on the relative movement amount.

In this aspect, the presence of articles trapped in the sealed portioncan be detected even when the mechanism, used as the drive source fordriving the sealing members, is incapable of perceiving the force/momentexerted on the film by the drive source via the sealing members andpositional information pertaining to the drive source (e.g., therotational angle of the motor, etc.), directly from information obtainedfrom the drive source.

In the packaging machine according to the present invention, the pair ofsealing members are preferably configured to be rotated in a circularorbit, whereby the sealing members sandwich and laterally seal the filmalong a direction intersecting a first direction, the film beingconveyed in the first direction and formed into a tubular shape.

In this aspect, in a packaging machine using a rotating lateral sealingmechanism, the presence of articles trapped in the sealed portion duringlateral sealing can be detected.

In the packaging machine according to the present invention, the firstand second support parts are preferably rotating shafts for rotating thesealing members.

In this aspect, in the packaging machine using a rotating lateralsealing mechanism, the presence of articles trapped in the sealedportion during lateral sealing can be detected by measuring the relativemovement amount of the rotating shafts for rotating the sealing members.

One possible method for detecting the presence of articles trapped inthe sealed portion is a method of measuring the relative movement amountof one sealing member in relation to the other sealing member. However,when the movement amount of sealing members to be rotated in a circularorbit is measured, the configuration for measuring the movement amountis likely to be complicated. In this aspect, because the relativemovement amount of the rotating shafts for rotating the sealing membersis measured, the presence of articles trapped in the sealed portion canbe detected with a simpler configuration than it is detected bymeasuring the movement amount of the sealing members.

The packaging machine according to the present invention is preferablyfurther provided with a fluid-pressure-utilizing pressing mechanism. Thefluid-pressure-utilizing pressing mechanism is preferably configured toconstantly presses the first support part toward the second support partso that the film is to be pressed between the sealing members when thefilm is sandwiched between the pair of sealing members.

The presence of articles trapped in the sealed portion can be detectedeven when an inexpensive fluid-pressure-utilizing pressing mechanism,which does not itself perceive the force/moment or the like exerted onthe film, is used in order to apply pressure to the film between thesealing members.

In the packaging machine according to the present invention, each of thefirst and second support parts is preferably configured to support thesealing member at a first-end side and a second-end side in thelongitudinal direction of a surface with which the sealing memberssandwich the film. The movement amount detector is preferably configuredto measure, as the relative movement amount, a first relative movementamount of the first support part in relation to the second support partat the first-end side, and a second relative movement amount of thefirst support part in relation to the second support part at thesecond-end side. The entrapment determination part is preferablyconfigured to determine whether or not articles are present in thesealed portion based on the first relative movement amount and thesecond relative movement amount.

In this aspect, when the first and second support parts support thesealing members at both ends in the longitudinal direction of thesurfaces with which the sealing members sandwich the film, the relativemovement amounts of the first support part in relation to the secondsupport part in the respective ends are used in the determination of thepresence of trapped articles. It is therefore easy to perceive thatarticles have been trapped regardless of the location in which they havebeen trapped in the sealed portion.

In the packaging machine according to the present invention, theentrapment determination part is preferably configured to determinewhether or not articles are trapped in the sealed portion based onstatistics of the relative movement amount measured during apredetermined time period by the movement amount detector.

In this aspect, erroneous detection of the presence of trapped articlesis minimized or eliminated, even if there is momentarily a comparativelylarge measurement error in the relative movement amount measured by themovement amount detector.

Furthermore, in the packaging machine according to the presentinvention, the entrapment determination part is preferably configured todetermine whether or not articles are present in the sealed portionbased on an average value of the relative movement amount measuredduring a predetermined time period by the movement amount detector.

In this aspect, erroneous detection of the presence of trapped articlesis minimized or eliminated even if there is momentarily a comparativelylarge measurement error in the relative movement amount measured by themovement amount detector, because the presence of trapped articles aredetermined based on the average value of the relative movement amount.

In the packaging machine according to the present invention, the pair ofsealing members are preferably configured to be rotated in a circularorbit, whereby the sealing members sandwich and laterally seal the filmalong a direction intersecting a first direction sequentially from theforward side in the first direction, the film being conveyed in thefirst direction and formed into a tubular shape. The entrapmentdetermination part is preferably configured to determine whether or notarticles are present in the sealed portion, both in a first time periodbeginning at a start of a sealing action by the sealing members andending at a first time point and in a second time period beginning at asecond time point after the first time point and ending at a finish ofthe sealing action, within the single sealing action.

In the packaging machine using a rotating lateral sealing mechanism, thedetermination of the presence of trapped articles is performedseparately at the sealing action starting time and the sealing actionfinishing time, within one sealing action. Therefore, when bags arebeing packaged continuously, a determination of the presence of trappedarticles of one-end side of one bag and a determination of the presenceof trapped articles of the other-end side of the following bag can beperformed separately. It is thereby easy to detect only bags in whichcaching of articles is actually caused.

In the packaging machine according to the present invention, the secondsupport part is preferably secured so as not to move in a directiontoward or away from the first support part. The first support part ispreferably capable of moving in a direction toward or away from thesecond support part. The movement amount detector is preferablyconfigured to measure the movement amount of the first support part inthe direction toward or away from the second support part as therelative movement amount when the first support part moves toward oraway from the second support part.

In this aspect, because only one support part can move toward or awayfrom the other support part and occurrence of the presence of articlestrapped in the sealed portion is determined by detecting the movementamount, the relative movement amount can be measured with a simpleconfiguration to detect the presence of trapped articles.

Advantageous Effects of Invention

In the packaging machine of the present invention, the presence ofarticles trapped in the sealed portion can be detected even when themechanism, used as the drive source for driving the sealing members, isincapable of perceiving the force/moment exerted on the film by thedrive source via the sealing members and positional informationpertaining to the drive source (e.g., the rotational angle of the motor,etc.), directly from information obtained from the drive source.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a weighing and packaging apparatusincluding a packaging machine (bag making and packaging machine)according to an embodiment of the present invention.

FIG. 2 is a block diagram of the weighing and packaging apparatusaccording to FIG. 1.

FIG. 3 is a perspective view showing the general configuration of thebag making and packaging unit of the bag making and packaging machineaccording to FIG. 1.

FIG. 4 is a side view, as seen from the right in FIG. 2, of the lateralsealing mechanism of the bag making and packaging unit according to FIG.3.

FIG. 5 is a side view, as seen from the right in FIG. 2, of the path ofthe sealing jaws of the lateral sealing mechanism according to FIG. 4.

FIG. 6 is a perspective view, as seen from the rear right in FIG. 2, ofthe horizontal-direction pressing mechanism of the lateral sealingmechanism according to FIG. 4.

FIG. 7 is a side view showing the condition in which the sealing actionis performed by the sealing jaws of the lateral sealing mechanismaccording to FIG. 4.

FIG. 8 is a perspective view showing the attaching manner of the rotaryencoder in the bag making and packaging mechanism according to FIG. 1.

FIG. 9 shows graphs showing the change over time in the movement amountof the first rotating shaft relative to the second rotating shaft,during the sealing action by the sealing jaws of the lateral sealingmechanism according to FIG. 4. FIG. 9(a) shows the change over time inthe movement amount of the first rotating shaft relative to the secondrotating shaft, when no articles are present in the sealed portion. FIG.9(b) shows the change over time in the movement amount of the firstrotating shaft relative to the second rotating shaft, when articles arepresent in the sealed portion within the time period X1.

FIG. 10 is a perspective view showing the attaching manner of the loadcell in the bag making and packaging machine according to ModificationA.

FIG. 11 is a perspective view showing the attaching manner of thepotentiometer in the bag making and packaging machine according toModification A.

FIG. 12 is a drawing showing the path of sealing jaws of a lateralsealing mechanism which performs D-shaped motion according toModification C.

DESCRIPTION OF EMBODIMENTS

An embodiment of the present invention is described below with referenceto the drawings. The following embodiment is a specific example of theembodiment of the present invention and is not intended to limit thetechnical scope of the present invention.

(1) Overall Configuration

FIG. 1 is a perspective view of a weighing and packaging apparatus 1including a bag making and packaging machine 3 according to anembodiment of the present invention. FIG. 2 is a block diagram of theweighing and packaging apparatus 1.

The weighing and packaging apparatus 1 has primarily a combinationweighing machine 2, the bag making and packaging machine 3, and acontroller 30 (see FIGS. 1 and 2). The bag making and packaging machine3 is provided with a bag making and packaging unit 3 a and a film supplyunit 3 b (see FIG. 1).

The combination weighing machine 2 is disposed above the bag making andpackaging unit 3 a. In the combination weighing machine 2, goods C(packaged goods) are weighed in a plurality of weighing hoppers, theweight values are combined so as to reach a predetermined total weight,and goods C having the combined predetermined total weight aredischarged downward.

The bag making and packaging unit 3 a of the bag making and packagingmachine 3 bags the goods C in accordance with the timing at which thegoods C are supplied from the combination weighing machine 2. The filmsupply unit 3 b supplies a film F for packaging, which will be formedinto a bag B, to the bag making and packaging unit 3 a.

The weighing and packaging apparatus 1 is provided with operationswitches 4 for operating the weighing and packaging apparatus 1. Theweighing and packaging apparatus 1 is provided with a touch paneldisplay 5 on which the operating state of the weighing and packagingapparatus 1 is displayed, and to which various settings for the weighingand packaging apparatus 1 are inputted. The operation switches 4 and thetouch panel display 5 function as input parts for receiving commands forthe combination weighing machine 2 and the bag making and packagingmachine 3, and/or settings pertaining to the combination weighingmachine 2 and the bag making and packaging machine 3. The touch paneldisplay 5 functions as an output part for displaying informationpertaining to the combination weighing machine 2 and the bag making andpackaging machine 3. In the present embodiment, the operation switches 4and the touch panel display 5 are shared by the combination weighingmachine 2 and the bag making and packaging machine 3 but are not limitedas such; operation switches and a touch panel display may be provided toeach machine.

The operation switches 4 and the touch panel display 5 are connected tothe controller 30, which is configured from a CPU, ROM, RAM and thelike. The controller 30 controls the combination weighing machine 2 andthe bag making and packaging machine 3 in accordance with operations andsettings inputted from the operation switches 4 and/or the touch paneldisplay 5. The controller 30 takes in necessary information from varioussensors arranged to the combination weighing machine 2 and the bagmaking and packaging machine 3, and uses this information to control thecombination weighing machine 2 and the bag making and packaging machine3. In the present embodiment, the controller 30 controls both thecombination weighing machine 2 and the bag making and packaging machine3. In other words, the controller 30 constitutes part of the combinationweighing machine 2 as a control part of the combination weighing machine2. The controller 30 also constitutes part of the bag making andpackaging machine 3 as a control part of the bag making and packagingmachine 3. The configuration is not limited to this example andrespective controllers may be provided to the combination weighingmachine 2 and the bag making and packaging machine 3.

(2) Detailed Configuration

The details of the bag making and packaging machine 3 and the controller30 will be described.

In the following description, the expressions “front (front surface),”“rear (back surface),” “up,” “down,” “left,” “right,” and the like aresometimes used in order to represent directions. The expressions “front(front surface),” “rear (back surface),” “up,” “down,” “left,” and“right” are defined as shown in FIG. 3. When not specified otherwise,the expressions “front (front surface),” “rear (back surface),” “up,”“down,” “left,” “right,” and the like are used according to how they aredefined in FIG. 3. The expressions “upstream” and “downstream” are alsosometimes used, and when not specified otherwise, the terms “upstream”and “downstream” use the conveying direction of the film F as astandard.

(2-1) Bag Making and Packaging Unit

The bag making and packaging unit 3 a is described below.

The bag making and packaging unit 3 a has primarily a forming mechanism13, a pull-down belt mechanism 14, a vertical sealing mechanism 15, alateral sealing mechanism 17, and a rotary encoder 40 (see FIGS. 2 and3).

The forming mechanism 13 forms the sheet-like film F, which is conveyedfrom the film supply unit 3 b, into a tube shape. The pull-down beltmechanism 14 downwardly conveys the film F formed into a tubular shape(hereinafter called the tubular film Fe). The vertical sealing mechanism15 vertically seals the overlapping portions (the seams) of the tubularfilm Fc. The lateral sealing mechanism 17 seals the upper and lower endsof the bag B by sealing (laterally sealing) the downwardly conveyedtubular film Fc along a direction intersecting the conveying direction.Further the lateral sealing mechanism 17 cut the laterally sealed bag Baway from the tubular film Fc with a knife 72 a arranged to sealing jaws51 b, 52 b, described hereinafter. The packaged bag B cut away from thetubular film Fc is discharged from the bottom of the bag making andpackaging machine 3. The rotary encoder 40 measures the amount ofmovement of a first rotating shaft 53 a of a first rotating body 50 a ofthe lateral sealing mechanism 17, described hereinafter (the amount ofrelative movement of the first rotating shaft 53 a in relation to asecond rotating shaft 53 b of a second rotating body 50 b of the lateralsealing mechanism 17, described hereinafter).

(2-1-1) Forming Mechanism

The forming mechanism 13 has a tube 13 b and a former 13 a.

The tube 13 b is a tubular member, open at the upper and lower ends. Thegoods C weighed by the combination weighing machine 2 are loaded intothe opening at the upper end of the tube 13 b.

The former 13 a is disposed so as to surround the tube 13 b. The film Fin sheet form unreeled from a film roll of the film supply unit 3 b isformed into a tube shape when passing between the former 13 a and thetube 13 b. The tube 13 b and the former 13 a of the forming mechanism 13can be replaced depending on the size of the bag B to be produced.

(2-1-2) Pull-Down Belt Mechanism

The pull-down belt mechanism 14 sticks to and continuously downwardlyconveys the tubular film Fc that is wound around the tube 13 b. Thepull-down belt mechanism 14 has a pair of belts 14 c disposed on theleft and right sides of the tube 13 b so as to sandwich the tube 13 b,as shown in FIG. 3. In the pull-down belt mechanism 14, the belts 14 c,which have a sucking function, are rotated by a drive roller 14 a and adriven roller 14 b, whereby the tubular film Fc is conveyed downward.FIG. 3 does not show a roller drive motor for rotating the drive roller14 a and the like.

(2-1-3) Vertical Sealing Mechanism

The vertical sealing mechanism 15 heat-seals the tubular film Fc in thevertical direction (in the up-down direction in FIG. 3).

The vertical sealing mechanism 15 is disposed on the front side of thetube 13 b (see FIG. 3). The vertical sealing mechanism 15 is driven inthe forward-backward direction by a drive mechanism (not shown) so as tomove toward the tube 13 b or move away from the tube 13 b. When thevertical sealing mechanism 15 is driven by the drive mechanism so as tomove toward the tube 13 b, the overlapping portions (the seams) of thetubular film Fc wound around the tube 13 b are sandwiched between thevertical sealing mechanism 15 and the tube 13 b. The vertical sealingmechanism 15 heats the overlapping portions of the tubular film Fc whilesandwiching them with the tube 13 b and thereby heat-seals them in thevertical direction.

(2-1-4) Lateral Sealing Mechanism

As will be described hereinafter, the lateral sealing mechanism 17 is amechanism in which the sealed portions of the downwardly conveyedtubular film Fc are sandwiched and laterally sealed along a direction(the left-right direction in this case) intersecting the conveyingdirection of the tubular film Fc, by a pair of sealing jaws 51 (asealing jaw 51 a and a sealing jaw 51 b), or a pair of sealing jaws 52(a sealing jaw 52 a and a sealing jaw 52 b).

The lateral sealing mechanism 17 has primarily a first rotating body 50a, a second rotating body 50 b, and a horizontal-direction pressingmechanism 56, as shown in FIG. 4. The first rotating body 50 a is placedon the front side of the tubular film Fc (the left side in FIG. 4). Thesecond rotating body 50 b is placed on the back side of the tubular filmFc (the right side in FIG. 4). As will be described hereinafter, whenthe tubular film Fc is sandwiched between the pair of sealing jaws 51 orthe pair of sealing jaws 52, the horizontal-direction pressing mechanism56 constantly presses the first rotating shaft 53 a of the firstrotating body 50 a toward the second rotating shaft 53 b of the secondrotating body 50 b (rearward) so that the tubular film Fc is to bepressed between the pair of sealing jaws 51 or the pair of sealing jaws52. In FIG. 4, the direction in which the first rotating shaft 53 a ispressed toward the second rotating shaft 53 b is shown by theright-pointing arrows A1.

(2-1-4-1) Rotating Bodies

The first rotating body 50 a and the second rotating body 50 b will bedescribed in detail.

(2-1-4-1-1) First Rotating Body

The first rotating body 50 a has primarily a first rotating shaft 53 a,a pair of levers 54 a, a pair of levers 55 a, the sealing jaw 51 a, andthe sealing jaw 52 a, as shown in FIG. 4.

The first rotating shaft 53 a is a rotating shaft of the first rotatingbody 50 a extending in the left-right direction. In a side view, thefirst rotating body 50 a rotates about a rotational axis C1 with thefirst rotating shaft 53 a as a rotating shaft (see FIG. 4).

The pair of levers 54 a are respectively connected near the longitudinalends (near the left-right directional ends) of the first rotating shaft53 a. Each of the levers 54 a extends from the first rotating shaft 53 ain the radial direction of the first rotating shaft 53 a. Each of thelever 54 a extends from the first rotating shaft 53 a in the samedirection and in parallel with the other lever 54 a.

The pair of levers 55 a are respectively connected near the longitudinalends (near the left-right directional ends) of the first rotating shaft53 a. Each of the levers 55 a extends from the first rotating shaft 53 ain the radial direction of the first rotating shaft 53 a. Each of thelevers 55 a extends from the first rotating shaft 53 a in the samedirection and in parallel with the other lever 55 a.

In a side view, the lever 54 a and the lever 55 a that are connectednear the right end of the first rotating shaft 53 a extend in pointsymmetry with respect to the rotational center C1 of the first rotatingbody 50 a (see FIG. 4). In other words, in a side view, the lever 54 aand the lever 55 a that are connected near the right end of the firstrotating shaft 53 a extend in opposite directions from the rotationalcenter C1 of the first rotating body 50 a (see FIG. 4). In a side view,the lever 54 a and the lever 55 a that are connected near the left endof the first rotating shaft 53 a extend in point symmetry with respectto the rotational center C1 of the first rotating body 50 a. In otherwords, in a side view, the lever 54 a and the lever 55 a that areconnected near the left end of the first rotating shaft 53 a extend inopposite directions from the rotational center C1 of the first rotatingbody 50 a.

The sealing jaw 51 a constitutes one of the pair of sealing jaws 51. Thesealing jaws 51 are an example of the sealing members. The sealing jaw51 a has a sealing surface 511 a (see FIG. 7) of which the left-rightdirection is the longitudinal direction.

The sealing jaw 51 a functions as a pair with the sealing jaw 51 bdescribed hereinafter, and seals the sealed portion of the tubular filmFc. More specifically, the sealing jaws 51 sandwich and laterally sealthe sealed portion of the tubular film Fc in the left-right direction(see FIG. 7), using the sealing surface 511 a of the sealing jaw 51 a ofwhich the left-right direction is the longitudinal direction and alater-described sealing surface 511 b of the sealing jaw 51 b of whichthe left-right direction is the longitudinal direction.

Both ends of the sealing jaw 51 a in the longitudinal direction (theleft-right direction) of the sealing surface 511 a are respectivelyconnected to the ends of the levers 54 a extending from the firstrotating shaft 53 a. Because the levers 54 a are connected to the firstrotating shaft 53 a as described above, the sealing jaw 51 a issupported by the first rotating shaft 53 a at both ends in thelongitudinal direction (the left-right direction) of the sealing surface511 a, via the pair of levers 54 a.

The sealing jaw 52 a constitutes one of the pair of sealing jaws 52. Thesealing jaws 52 are an example of the sealing members. The sealing jaw52 a has a sealing surface (not shown) of which the left-right directionis the longitudinal direction.

The sealing jaw 52 a functions as a pair with the sealing jaw 52 bdescribed hereinafter, and seals the sealed portion of the tubular filmFc. More specifically, the sealing jaws 52 sandwich and laterally sealthe sealed portion of the tubular film Fc in the left-right direction,using the sealing surface of the sealing jaw 51 a of which theleft-right direction is the longitudinal direction and a later-describedsealing surface (not shown) of the sealing jaw 51 b of which theleft-right direction is the longitudinal direction.

Both ends of the sealing jaw 52 a in the longitudinal direction (theleft-right direction) of the sealing surface are respectively connectedto the ends of the levers 55 a extending from the first rotating shaft53 a. Because the levers 55 a are connected to the first rotating shaft53 a as described above, the sealing jaw 52 a is supported by the firstrotating shaft 53 a at both ends in the longitudinal direction (theleft-right direction) of its sealing surface, via the pair of levers 55a. Because the levers 54 a and the levers 55 a extend in oppositedirections from the rotational center C1 of the first rotating body 50 ain a side view, the sealing jaw 52 a is disposed in a position 180° awayfrom the sealing jaw 51 a about the rotational center C1 of the firstrotating body 50 a.

(2-1-4-1-2) Second Rotating Body

The second rotating body 50 b has primarily the second rotating shaft 53b, a pair of levers 54 b, a pair of levers 55 b, the sealing jaw 51 b,and the sealing jaw 52 b, as shown in FIG. 4.

The second rotating shaft 53 b is a rotating shaft of the secondrotating body 50 b extending in the left-right direction. In a sideview, the second rotating body 50 b rotates about a rotational center C2with the second rotating shaft 53 b as the rotating shaft (see FIG. 4).

The pair of levers 54 b are respectively connected near the longitudinalends (near the left-right directional ends) of the second rotating shaft53 b. Each of the levers 54 b extends from the second rotating shaft 53b in the radial direction of the second rotating shaft 53 b. Each of thelevers 54 b extends from the second rotating shaft 53 b in the samedirection and in parallel with the other lever 54 b.

The pair of levers 55 b are respectively connected near the longitudinalends (near the left-right directional ends) of the second rotating shaft53 b. Each of the levers 55 b extends from the second rotating shaft 53b in the radial direction of the second rotating shaft 53 b. Each of thelevers 55 b extends from the second rotating shaft 53 b in the samedirection and in parallel with the other lever 55 b.

In a side view, the lever 54 b and the lever 55 b that are connectednear the right end of the second rotating shaft 53 b extend in pointsymmetry with respect to the rotational center C2 of the second rotatingbody 50 b (see FIG. 4). In other words, in a side view, the lever 54 band the lever 55 b that are connected near the right end of the secondrotating shaft 53 b extend in opposite directions from the rotationalcenter C2 of the second rotating body 50 b (see FIG. 4). In a side view,the lever 54 b and the lever 55 b that are connected near the left endof the second rotating shaft 53 b extend in point symmetry with respectto the rotational center C2 of the second rotating body 50 b. In otherwords, in a side view, the lever 54 b and the lever 55 b that areconnected near the left end of the second rotating shaft 53 b extend inopposite directions from the rotational center C2 of the second rotatingbody 50 b.

The sealing jaw 51 b constitutes one of the pair of sealing jaws 51. Thesealing jaw 51 b has a sealing surface 511 b (see FIG. 7) of which theleft-right direction is the longitudinal direction. The sealing jaw 51 bfunctions as a pair with the sealing jaw 51 a as previously described,and seals the sealed portion of the tubular film Fc.

Both ends of the sealing jaw 51 b in the longitudinal direction (theleft-right direction) of the sealing surface 511 b are respectivelyconnected to the ends of the levers 54 b extending from the secondrotating shaft 53 b. Because the levers 54 b are connected to the secondrotating shaft 53 b as described above, the sealing jaw 51 b issupported by the second rotating shaft 53 b at both ends in thelongitudinal direction (the left-right direction) of the sealing surface511 b, via the pair of levers 54 b.

The sealing jaw 52 b constitutes one of the pair of sealing jaws 52. Thesealing jaw 52 b has a sealing surface (not shown) of which theleft-right direction is the longitudinal direction. The sealing jaw 52 bfunctions as a pair with the sealing jaw 52 a as previously described,and seals the sealed portion of the tubular film Fc.

Both ends of the sealing jaw 52 b in the longitudinal direction (theleft-right direction) of the sealing surface are respectively connectedto the ends of the levers 55 b extending from the second rotating shaft53 b. Because the levers 55 b are connected to the second rotating shaft53 b as described above, the sealing jaw 52 b is supported by the secondrotating shaft 53 b at both ends in the longitudinal direction (theleft-right direction) of its sealing surface, via the pair of levers 55b. Because the levers 54 b and the levers 55 b extend in oppositedirections from the rotational center C2 of the second rotating body 50b in a side view, the sealing jaw 52 b is disposed in a position 180°away from the sealing jaw 51 b about the rotational center C2 of thesecond rotating body 50 b.

(2-1-4-1-3) Operation of First and Second Rotating Bodies

The first rotating shaft 53 a is driven by a drive motor (not shown),whereby the first rotating body 50 a is to be rotated about therotational center C1 in a side view (see FIG. 5). The second rotatingshaft 53 b is driven by a drive motor (not shown), whereby the secondrotating body 50 b is to be rotated about the rotational center C2 in aside view (see FIG. 5). This causes the sealing jaw 51 a and the sealingjaw 52 a to rotate in a circular orbit about the rotational center C1,and the sealing jaw 51 b and the sealing jaw 52 b to rotate in acircular orbit about the rotational center C2 (see FIG. 5). The firstrotating body 50 a, when viewed from the right side, is to be rotatedclockwise about the rotational center C1 (see FIG. 5). In other words,the sealing jaw 51 a and the sealing jaw 52 a, when viewed from theright side, are to be rotated clockwise about the rotational center C1.The second rotating body 50 b, when viewed from the right side, is to berotated counterclockwise about the rotational center C2 (see FIG. 5). Inother words, the sealing jaw 51 b and the sealing jaw 52 b, when viewedfrom the right side, are to be rotated counterclockwise about therotational center C2.

The first rotating body 50 a is supported at both ends in the lateralsealing direction (in the left-right direction) by horizontally movingplates 61 (see FIG. 4). More specifically, both ends in the left-rightdirection of the first rotating shaft 53 a of the first rotating body 50a are supported by the horizontally moving plates 61. The secondrotating body 50 b is supported at both ends in the lateral sealingdirection (in the left-right direction) by stationary plates 62 (seeFIG. 4). More specifically, both ends in the left-right direction of thesecond rotating shaft 53 b of the second rotating body 50 b aresupported by the stationary plates 62. The stationary plates 62 aresecured to a frame 63 (see FIG. 6) of the bag making and packaging unit3 a.

The horizontally moving plates 61 are pressed toward the stationaryplates 62 by the horizontal-direction pressing mechanism 56 (refer tothe arrows A1 in FIG. 4). As a result, the first rotating shaft 53 asupported on the horizontally moving plates 61 is pressed by thehorizontal-direction pressing mechanism 56 toward the second rotatingshaft 53 b supported on the stationary plates 62.

(2-1-4-2) Horizontal-Direction Pressing Mechanism

The horizontal-direction pressing mechanism 56 will be described. Thehorizontal-direction pressing mechanism 56 is an example of afluid-pressure-utilizing mechanism.

The horizontal-direction pressing mechanism 56 utilizes air pressure topress the first rotating shaft 53 a toward the second rotating shaft 53b. The horizontal-direction pressing mechanism 56 utilizes air pressurein this embodiment, but the configuration is not limited to this, andmay utilize, e.g., oil pressure.

The horizontal-direction pressing mechanism 56 has primarily an aircylinder 80, a first linking rod 81, a linking plate 82, and secondlinking rods 83, as shown in FIG. 4.

The air cylinder 80 is driven by air pressure. The air cylinder 80 isconnected with the linking plate 82 via the first linking rod 81 whichextends rearward from the air cylinder 80. When the air cylinder 80 isdriven, force is transferred via the first linking rod 81, and thelinking plate 82 is pressed rearward. In FIG. 4, the direction in whichthe linking plate 82 is pressed is indicated by the right-pointingarrows A1.

The second linking rods 83 are rod-shaped members connecting the linkingplate 82 and the horizontally moving plates 61. The horizontal-directionpressing mechanism 56 has four second linking rods 83. One end of eachsecond linking rod 83 is connected with the linking plate 82. Two of thesecond linking rods 83 extend forward in parallel from the upper-rightcorner vicinity and the lower-right corner vicinity of the linking plate82, as shown in FIG. 6. Though not illustrated, the other two secondlinking rods 83 extend forward in parallel from the upper-left cornervicinity and the lower-left corner vicinity of the linking plate 82. Thetwo second linking rods 83 that extend forward from the right-side endvicinities of the linking plate 82 are connected with the horizontallymoving plate 61 disposed on the right side of the first rotating body 50a. The two second linking rods 83 that extend forward from the left-sideend vicinities of the linking plate 82 are connected with thehorizontally moving plate 61 disposed on the left side of the firstrotating body 50 a. The second linking rods 83 are not connected withthe stationary plates 62, but the second linking rods 83 slideablyextend through the stationary plates 62. The end (front-side end)vicinities of the second linking rods 83 on the side opposite thelinking plate 82 are slideably supported by rod support members 83 asecured to the frame 63 of the bag making and packaging unit 3 a.Because the second linking rods 83 are slideably supported by the rodsupport members 83 a, the horizontally moving plates 61 connected withthe second linking rods 83 can move toward or away from the stationaryplates 62. In other words, the first rotating shaft 53 a supported onthe horizontally moving plates 61 can move toward or away from thesecond rotating shaft 53 b supported on the stationary plates 62. Thefirst rotating shaft 53 a moves toward or away from the second rotatingshaft 53 b according to the balance between the force from the aircylinder 80 and the force exerted either by the sealing jaw 51 b on thesealing jaw 51 a, or by the sealing jaw 52 b on the sealing jaw 52 a,when the tubular film Fc is being laterally sealed by the sealing jaws51 or the sealing jaws 52.

(2-1-4-3) Sealing Action by Sealing Jaws

Next, the sealing action by the sealing jaws 51 will be described. Morespecifically, the following is a description of the lateral sealing ofthe tubular film Fc by the sealing jaws 51 during the sealing action bythe sealing jaws 51, and the cutting of the laterally sealed bag B awayfrom the tubular film Fc in the sealing jaws 51.

The rotating of the first rotating body 50 a and the second rotatingbody 50 b (the rotational direction is indicated by the arrows depictedin two-dot chain lines in FIG. 5) and the pressing of the first rotatingshaft 53 a toward the second rotating shaft 53 b by thehorizontal-direction pressing mechanism 56 (the pressing direction isindicated by the arrow A2 depicted below the first rotating body 50 a inFIG. 5) cause the sealing jaw 51 a and the sealing jaw 51 b to sandwichand apply pressure to the downwardly conveyed tubular film Fc betweenthe sealing surface 511 a of the sealing jaw 51 a and the sealingsurface 511 b of the sealing jaw 51 b (see FIG. 7). The sealing surface511 a and the sealing surface 511 b have serrations 512 a and serrations512 b which mesh with each other, as shown in FIG. 7. The sealing jaws51 sandwich the tubular film Fc so that the teeth of the serrations 512a in the sealing surface 511 a and the teeth of the serrations 512 b inthe sealing surface 511 b mesh each other and apply pressure to thetubular film Fc. The sealing jaw 51 a and the sealing jaw 51 b haveheaters 71 (see FIG. 7) arranged in the interiors, and the sealingsurface 511 a and sealing surface 511 b are heated by these heaters 71.The sealing surface 511 a and the sealing surface 511 b are heated whilethe tubular film Fc is sandwiched by the sealing surface 511 a and thesealing surface 511 b, the sealed portion of the tubular film Fc isthereby heat-sealed. The downwardly conveyed tubular film Fc isheat-sealed in order from the downstream side (the forward side in theconveying direction) toward the upstream side (the rearward side in theconveying direction).

In the sealing jaw 51 b, a knife 72 a for cutting the bag B away fromthe tubular film Fc is disposed near the middle of the sealing surface511 b in the transverse direction (a direction orthogonal to thelongitudinal direction of the sealing surface 511 b). The knife 72 a isdisposed so that the blade tip protrudes on the side of the sealing jaw51 a during the sealing action by the sealing jaw 51 a and the sealingjaw 51 b (see FIG. 7). In the sealing jaw 51 a, a groove 72 b, withwhich the knife 72 a protruding from the sealing jaw 51 b toward thesealing jaw 51 a meshes, is formed near the middle of the sealingsurface 511 a in the transverse direction (a direction orthogonal to thelongitudinal direction of the sealing surface 511 a). The knife 72 a,which is formed into a slanted blade, cuts the bag B away from thetubular film Fc from one end side toward the other end side in thelateral sealing direction (the left-right direction).

Because the knife 72 a is disposed near the middle of the sealingsurface 511 b of the sealing jaw 51 b in the transverse direction, thesealing jaws 51 perform the following actions in order as single sealingaction:

(1) Laterally sealing the tubular film Fc

(2) Cutting the transversely sealed bag B away from the tubular film Fcusing the knife 72 a on the upstream side of the position laterallysealed in (1)

(3) Laterally sealing the tubular film Fc on the upstream side of theposition cut by the knife 72 a in (2)

However, the timing with which lateral sealing or cutting of the tubularfilm Fc is performed by one set of actions (1) to (3) may partiallyoverlap the timing with which another set of actions (1) to (3) isperformed. In other words, cutting of the tubular film Fc in (2) maybegin at a timing when lateral sealing in (1) is not completelyfinished, and lateral sealing in (3) may begin when cutting of thetubular film Fc in (2) is not finished.

Lateral sealing of the tubular film Fc by the sealing jaws 52 andcutting the laterally sealed bag B away from the tubular film Fc in thesealing jaws 52 are similar to those actions of the sealing jaws 51, andare therefore not described here.

(2-1-5) Rotary Encoder

The rotary encoder 40 is one example of a movement amount detector. Therotary encoder 40 is secured to the frame 63 of the bag making andpackaging unit 3 a (see FIG. 8). A rotating shaft of the rotary encoder40 is engaged with the forward-side (the side opposite to the sideconnected with the linking plate 82) end part of the second linking rod83 so as to rotate due to the second linking rod 83 moving forward andbackward. Two rotary encoders 40 are provided. The rotating shaft of onerotary encoder 40 is engaged with the end part of the second linking rod83 that, among the four second linking rods 83, is located on the upperright side. The rotating shaft of the other rotary encoder 40 is engagedwith the end part of the second linking rod 83 that is located on theupper left side. The arrangement is not limited to this example, and therotating shaft of one rotary encoder 40 may be engaged with the end partof the second linking rod 83 located on the lower right side, while therotating shaft of the other rotary encoder 40 may be engaged with theend part of the second linking rod 83 located on the lower left side.

The rotary encoders 40 measure the forward and backward movement amountof the second linking rods 83 by measuring the rotational angles of therotating shafts of the rotary encoders 40. The forward and backwardmovement amount of the second linking rods 83 is equal to the amount bywhich the first rotating shaft 53 a, attached to the horizontally movingplates 61 connected to the second linking rods 83, moves relative to thesecond rotating shaft 53 b attached to the stationary plates 62. Inother words, the rotary encoders 40 measure the amount by which thefirst rotating shaft 53 a moves relative to the second rotating shaft 53b in the direction that the first rotating shaft 53 a moves eithertoward or away from the second rotating shaft 53 b, by measuring therotational angles of the rotating shafts of the rotary encoders 40.

The movement amount of the second linking rods 83 connected to thehorizontally moving plate 61 disposed on the right side of the firstrotating shaft 53 a, and the movement amount of the second linking rods83 connected to the horizontally moving plate 61 disposed on the leftside of the first rotating shaft 53 a, are measured by the rotaryencoders 40 as described above. In other words, the movement amount(right-side movement amount) of the first rotating shaft 53 a on theside of the right-side end part relative to the second rotating shaft 53b, and the movement amount (left-side movement amount) of the firstrotating shaft 53 a on the side of the left-side end part relative tothe second rotating shaft 53 b, are measured by the rotary encoders 40.Therefore, the movement of either the left or right end part of thefirst rotating shaft 53 a, toward or away from the second rotating shaft53 b, can be detected.

(2-2) Film Supply Unit

The film supply unit 3 b is a unit for supplying the film F in sheetshape to the forming mechanism 13 of the bag making and packaging unit 3a. The film supply unit 3 b is arranged adjacent to the bag making andpackaging unit 3 a. A roll around which the film F is wound is set inthe film supply unit 3 b, and the film F is unreeled from this roll.

(2-3) Controller

The controller 30 includes primarily a CPU, ROM, RAM, and other storagemedia. The controller 30, which is connected to the components of thecombination weighing machine 2, constitutes part of the combinationweighing machine 2 as a control part of the combination weighing machine2. The controller 30 is also connected (see FIG. 2) with the components(primarily, the drive motors for driving the pull-down belt mechanism14, the vertical sealing mechanism 15, and the first and second rotatingshafts 53 a, 53 b; the lateral sealing mechanism 17 having the aircylinder 80 of the horizontal-direction pressing mechanism 56 and othercomponents; the rotary encoders 40 (the right and left sides); and thefilm supply unit 3 b) of the bag making and packaging machine 3. Thecontroller 30 constitutes part of the bag making and packaging machine 3as a control part of the bag making and packaging machine 3. Thecontroller 30 controls the combination weighing machine 2 and the bagmaking and packaging machine 3 by executing programs stored in thestorage media.

The controller 30 controls the movement of the combination weighingmachine 2 and the bag making and packaging machine 3 so that, e.g., thecombination weighing machine 2 and the bag making and packaging machine3 perform the following actions.

The controller 30 controls the combination weighing machine 2 so thatthe weight of the goods C as the packaged goods is weighed by aplurality of weighing hoppers, these weight values are combined so as toreach a predetermined total weight, and a combined predetermined totalweight of goods C is discharged downward in the combination weighingmachine 2. The goods C discharged from the combination weighing machine2 are dropped into a top open end of the tube 13 b of the bag making andpackaging machine 3.

As a control part for controlling the bag making and packaging machine3, the controller 30 controls the film supply unit 3 b so that the filmF is supplied to the forming mechanism 13. As a control part forcontrolling the bag making and packaging machine 3, the controller 30also controls the pull-down belt mechanism 14 so that the film F formedinto a tube shape by the forming mechanism 13 (the tubular film Fc) isconveyed downward, and controls the vertical sealing mechanism 15 sothat the seams of the conveyed tubular film Fc are vertically sealed. Asa control part for controlling the bag making and packaging machine 3,the controller 30 also controls the lateral sealing mechanism 17 so thatthe downwardly conveyed tubular film Fc is sealed in the lateraldirection and the sealed bag B is cut away from the tubular film Fc onthe upstream side, in conformity with the timing at which the goods Cdischarged from the combination weighing machine 2 are discharged fromthe bottom open end of the tube 13 b.

The controller 30 has an entrapment determination part 30 a as afunctional part for controlling the bag making and packaging machine 3.Based on the amount (the right-side movement amount and left-sidemovement amount) by which the first rotating shaft 53 a moves relativeto the second rotating shaft 53 b, which is measured by the rotaryencoders 40, the entrapment determination part 30 a determines whetheror not any articles have been trapped in the sealed portion of thetubular film Fc when the sealing jaws 51, 52 laterally seal the film.The presence of articles trapped in the sealed portion of the tubularfilm Fc occurs when, e.g., when goods C are sandwiched in the sealedportion, and/or when cutting debris of the tubular film Fc aresandwiched in the sealed portion. The action to determine the presenceof trapped articles performed by the entrapment determination part 30 ais described hereinafter.

(3) Determination of Whether or Not Articles Are Present in SealedPortion

The determination of whether or not articles are present in the sealedportion of the tubular film Fc is described below.

(3-1) Change in Movement Amount of First Rotating Shaft Relative toSecond Rotating Shaft During Sealing Action

Firstly, how the change in the movement amount of the first rotatingshaft 53 a relative to the second rotating shaft 53 b during the sealingaction by the sealing jaws 51 differs between cases when no articles arepresent in the sealed portion and cases when articles are trapped in thesealed portion, is described referring to FIG. 9. As an example, themovement amount of the right-side end of the first rotating shaft 53 awill be described. The movement amount of the left-side end of the firstrotating shaft 53 a can be similarly described and is therefore notdescribed here. Further, as an example, the sealing action by thesealing jaws 51 will be explained. The sealing action by the sealingjaws 52 can be similarly described and is therefore not described here.

The numerical values of the amount of displacement indicated on thevertical axes of the graphs shown in FIGS. 9(a) and 9(b) are merelyspecific examples of cases when the settings of the lateral sealingmechanism 17 are adjusted to certain conditions, and these numericalvalues are not limited to these examples. The numerical values of theamount of displacement change depending on the settings of the lateralsealing mechanism 17.

(3-1-1) When No Articles Are Present in Sealed Portion

FIG. 9(a) is a graph of the change in the movement amount of the firstrotating shaft 53 a relative to the second rotating shaft 53 b when noarticles are present in the sealed portion of the tubular film Fe. InFIG. 9(a), the horizontal axis indicates time, and the vertical axisindicates movement amount [mm]. The movement amount in the direction inwhich the first rotating shaft 53 a moves away from the second rotatingshaft 53 b is represented by a positive value, and the movement amountin the direction in which the first rotating shaft 53 a moves toward thesecond rotating shaft 53 b is represented by a negative value.

The time period Y1 in FIG. 9(a) is a time period that precedes the startof the sealing action by the sealing jaws 51. Because the sealing actionis not performed by the sealing jaws 51 in the time period Y1 (nor isthe sealing action by the sealing jaws 52 performed), no particularforce acts on the first rotating shaft 53 a in the direction away fromthe second rotating shaft 53 b. The movement amount of the firstrotating shaft 53 a in the time period Y1 indicates a negative valuenear 0. In the graph of FIG. 9(a), a reference point of the movementamount of the first rotating shaft 53 a is taken so that the movementamount of the first rotating shaft 53 a when the sealing action is notperformed by the lateral sealing mechanism 17 is a value near 0.

The time period X1 in FIG. 9(a) is a period after the sealing action bythe sealing jaws 51 has begun and lateral sealing of the tubular film Fchas begun. Furthermore, the time period X1 extends up to the point intime when cutting of the tubular film Fc by the knife 72 a arranged tothe sealing jaw 51 b is started. The time period X1 is an example of thefirst time period. During the time period X1, the lower side of thesealing surface 511 a of the sealing jaw 51 a and the lower side of thesealing surface 511 b of the sealing jaw 51 b sandwich the tubular filmFc. Since the sealing jaw 51 a attached to the first rotating body 50 ais pushed by the sealing jaw 51 b attached to the second rotating body50 b secured to the frame 63 via the stationary plates 62, the firstrotating shaft 53 a moves away from the second rotating shaft 53 b. Inthe time period X1, the first rotating shaft 53 a moves a distance ofapproximately 0.1 mm at maximum from the reference point in thedirection away from the second rotating shaft 53 b (see FIG. 9(a)).

The time period X3 in FIG. 9(a) starts at the point in time when thetubular film Fc begins to be cut by the knife 72 a arranged to thesealing jaw 51 b, and ends at the point in time when the tubular film Fcfinishes being cut by the knife 72 a. When the tubular film Fc is cut bythe knife 72 a in the time period X3, a force greater than that duringlateral sealing is exerted by the sealing jaw 51 b on the sealing jaw 51a, and the first rotating shaft 53 a therefore moves even further awayfrom the second rotating shaft 53 b than in the time period X1. In thetime period X3, the first rotating shaft 53 a moves a distance ofapproximately 0.2 mm at maximum from the reference point in thedirection away from the second rotating shaft 53 b (see FIG. 9(a)).

The time period X2 in FIG. 9(a) starts at the point in time when thetubular film Fc has finished being cut by the knife 72 a arranged to thesealing jaw 51 b, and ends when the sealing jaws 51 finish laterallysealing the tubular film Fc on the upstream side of the position cut bythe knife 72 a (this time period lasts until the sealing jaws 51complete the sealing action). The time period X2 is one example of thesecond time period. In the time period X2, the upper side of the sealingsurface 511 a of the sealing jaw 51 a and the upper side of the sealingsurface 511 b of the sealing jaw 51 b sandwich the tubular film Fc, andthe sealing jaws 51 a is pushed by the sealing jaw 51 b similar to thetime period X1. However, the force with which the sealing jaw 51 a ispushed by the sealing jaw 51 b is less in the time period X2 than in thetime period X3 when the tubular film Fc is cut by the knife 72 a, andthe first rotating shaft 53 a therefore moves nearer to the secondrotating shaft 53 b than in the time period X3. In the time period X2,the first rotating shaft 53 a moves a distance of approximately 0.1 mmat maximum from the reference point in the direction away from thesecond rotating shaft 53 b (see FIG. 9(a)).

The time period Y2 in FIG. 9(a) is the time period after the sealingaction by the sealing jaws 51 is finished. Because the sealing action isnot performed by the sealing jaws 51 (nor is the sealing actionperformed by the sealing jaws 52) in the time period Y2, no particularforce acts on the first rotating shaft 53 a in the direction away fromthe second rotating shaft 53 b. The movement amount of the firstrotating shaft 53 a in the time period Y2 indicates a negative valuenear 0.

(3-1-2) When Articles Are Present in the Sealed Portion

Next, the change in the movement amount of the first rotating shaft 53 arelative to the second rotating shaft 53 b in a case when articles aretrapped in the sealed portion, and particularly in a case when articlesare trapped in the sealed portion during the lateral sealing in the timeperiod X1, is described referring to FIG. 9(b). In FIG. 9(b), thehorizontal and vertical axes are defined in the same manner as in FIG.9(a). The time periods Y1, Y2 and the time periods X1, X3, X2 are alsodefined in the same manner in FIG. 9(b).

The time period Y1 is the same as when no articles are trapped in thesealed portion and is therefore not described.

During the lateral sealing performed in the time period X1, becausearticles are present in the sealed portion of the tubular film Fe, thesealing jaw 51 a is pressed more strongly by the sealing jaw 51 b thanwhen no articles are present in the sealed portion. Therefore, whenarticles are present in the sealed portion during the lateral sealingperformed in the time period X1, the movement amount of the firstrotating shaft 53 a relative to the second rotating shaft 53 b isgreater than when no articles are trapped in the sealed portion. Forexample, the maximum value of the movement amount of the first rotatingshaft 53 a relative to the second rotating shaft 53 b in the time periodX1 is close to the maximum value of the movement amount in the timeperiod X3.

In the time period X3, the shape of the graph is different from FIG.9(a) because movement amount of the first rotating shaft 53 a relativeto the second rotating shaft 53 b in the time period X1 is larger.However, since large force is exerted on the sealing jaw 51 a by thesealing jaw 51 b when the tubular film Fc is cut by the knife 72 a, thefirst rotating shaft 53 a moves far away from the second rotating shaft53 b the same as in FIG. 9(a). In the time period X3, the first rotatingshaft 53 a moves a distance of approximately 0.2 mm at maximum from thereference point in the direction away from the second rotating shaft 53b (see FIG. 9(b)).

Regarding the time period X2 and the time period Y2, the graph in a casewhen articles are trapped in the sealed portion is the same that in acase when no articles are trapped in the sealed portion, and istherefore not described.

Although a detailed description is not given, when articles are trappedin the sealed portion during lateral sealing not in the time period X1but in the time period X2, a graph of the movement amount of the firstrotating shaft 53 a having following characteristics is obtained.

The movement amount of the first rotating shaft 53 a in the time periodsX1 and X3 is the same as the movement amount of the first rotating shaft53 a in the time periods X1 and X3 in FIG. 9(a). The movement amount ofthe first rotating shaft 53 a in the time period X2 exhibits the sametendency as the movement amount of the first rotating shaft 53 a in thetime period X1 in FIG. 9(b). In other words, the movement amount of thefirst rotating shaft 53 a in the time period X2 is greater than themovement amount of the first rotating shaft 53 a in the time period X3in FIG. 9(a).

(3-2) Action of Determining Whether or Not Articles Are Present inSealed Portion by the Entrapment Determination Part

The entrapment determination part 30 a determines whether or notarticles are present in the following manner, utilizing the differencein the movement amount of the first rotating shaft 53 a relative to thesecond rotating shaft 53 b between a case of no articles being presentin the sealed portion, and a case of articles being present in thesealed portion, as described above.

Because there is a possibility that articles are present in both thetime period X1 and the time period X2, the entrapment determination part30 a determines whether or not any articles are present for the timeperiod X1 and the time period X2. A case in which the entrapmentdetermination part 30 a determines whether or not any articles arepresent in the time period X1 is used as an example for thisdescription.

A default value, a maximum value Dmax (see FIG. 9) that the movementamount of the first rotating shaft 53 a could take when the entrapmentof articles is not caused, is given to the entrapment determination part30 a. The maximum value need not be the default value, and theentrapment determination part 30 a may, e.g., measure and accumulatemovement amounts of the first rotating shaft 53 a in a case when thetrapping of articles is not caused and calculate the maximum value Dmaxbased on the accumulated data.

The entrapment determination part 30 a obtains measured values from thetwo rotary encoders 40 and calculates the average of the movement amountof the first rotating shaft 53 a during the time period X1.Particularly, average value of the movement amount (right-side movementamount) of the right-side end of the first rotating shaft 53 a relativeto the second rotating shaft 53 b, and average value of the movementamount (the left-side movement amount) of the left-side end of the firstrotating shaft 53 a relative to the second rotating shaft 53 b arerespectively calculated.

The entrapment determination part 30 a compares the calculated averagevalue of the right-side movement amount and the average value of theleft-side movement amount with the maximum value Dmax that the movementamount of the first rotating shaft 53 a could take when no articles aretrapped, and determines that articles have been trapped in the timeperiod X1 when either average value is greater than the maximum valueDmax. When both average values are equal to or less than the maximumvalue Dmax, it is determined that no articles have been trapped in thetime period X1.

(3-3) Control of Bag Making and Packaging Machine When It Is DeterminedThat Articles Are Present

When it is determined by the entrapment determination part 30 a thatarticles have been trapped in the time period X1, the controller 30discharges the bag B, which is laterally sealed in the time period X1and cut away from the tubular film Fc in the subsequent time period X3,from the bag making and packaging machine 3 as a defective product,since there is a risk of a sealing defect. The bag B discharged as adefective product from the bag making and packaging machine 3 isconveyed to, e.g., a defective product collecting location by a conveyor(not shown). When it is determined by the entrapment determination part30 a that articles have been trapped in the time period X2, thecontroller 30 discharges the bag B, which is cut away during the sealingaction by the sealing jaws 52 in succession with the sealing action bythe sealing jaws 51, from the bag making and packaging machine 3 as adefective product since there is a risk of a sealing defect.

The control performed by the controller 30 when it is determined by theentrapment determination part 30 a that articles have been trapped inthe sealed portion of the tubular film Fc, is not limited to what isdescribed above. For example, when it is determined that articles havebeen trapped, instead of controlling as described above, the controller30 controls so that compressed air is vented out from the air cylinder80 and either the sealing jaw 51 a and sealing jaw 51 b or the sealingjaw 52 a and sealing jaw 52 b are moved away from each other at thetiming when the bag B having a risk of incomplete lateral sealing is tobe cut, so as not to cut away the bag B having a risk of incompletelateral sealing from the tubular film Fc.

(4) Characteristics

The characteristics of the bag making and packaging machine 3 accordingto the present embodiment are described below.

For the sake of convenience in the description, the characteristics ofthe bag making and packaging machine 3 are described using thedescription of the pair of sealing jaws 51 (the sealing jaws 51 a, 51b), but the characteristics of the bag making and packaging machine 3could be described in the same manner using the description of the pairof sealing jaws 52.

(4-1)

In the bag making and packaging machine 3 according to the presentembodiment, a pair of sealing jaws 51 sandwiches and seals the sealedportion of the tubular film Fc. The bag making and packaging machine 3is provided with the first rotating shaft 53 a as an example of a firstsupport part, the second rotating shaft 53 b as an example of a secondsupport part, the rotary encoders 40 as an example of a movement amountdetector, and the entrapment determination part 30 a. The first rotatingshaft 53 a supports one sealing jaw 51 (the sealing jaw 51 a), and thesecond rotating shaft 53 b supports the other sealing jaw 51 (thesealing jaw 51 b). The rotary encoders 40 measure the relative movementamount of the first rotating shaft 53 a in relation to the secondrotating shaft 53 b in an approaching direction or a moving awaydirection (in the present embodiment, movement amount of the firstrotating shaft 53 a is measured because the second rotating shaft 53 bdoes not move in an approaching direction or moving away direction fromthe first rotating shaft 53 a) when the first rotating shaft 53 a andthe second rotating shaft 53 b approach or move away. The entrapmentdetermination part 30 a determines whether or not articles are presentin the sealed portion based on the measured movement amount.

Here, the presence of articles in the sealed portion can be detectedeven when the drive source for driving the sealing jaws 51 (a rotationmotor for rotating the sealing jaws 51, and/or a horizontal-directionpressing mechanism 56 for pressing the sealing jaw 51 a against thesealing jaw 51 b) is a mechanism incapable of perceiving theforce/moment exerted by the drive source on the tubular film Fc via thesealing jaws 51, and positional information pertaining to the drivesource (e.g., the rotational angle of the motor or the like), directlyfrom information obtained from the drive source. In other words, thepresence of articles trapped in the sealed portion can be detectedwithout using an expensive configuration such as a servo motor as thedrive source.

(4-2)

In the bag making and packaging machine 3 according to the presentembodiment, the pair of sealing jaws 51 sandwich and laterally seal thetubular film Fc, which is conveyed in a first direction (downward in thepresent embodiment), along a direction (the left-right direction in thepresent embodiment) intersecting the first direction, due to the sealingjaws 51 a, 51 b being rotated along a circular orbit.

Here, in the bag making and packaging machine 3 using a rotating lateralsealing mechanism, the presence of articles trapped in the sealedportion during lateral sealing can be detected.

(4-3)

In the bag making and packaging machine 3 according to the presentembodiment, the first and second support parts are the first rotatingshaft 53 a and the second rotating shaft 53 b for rotating the sealingjaws 51.

Here, in the bag making and packaging machine 3 using a rotating lateralsealing mechanism, presence of articles trapped in the sealed portionduring lateral sealing can be detected by measuring the relativemovement amount of the first rotating shaft 53 a and the second rotatingshaft 53 b (in the present embodiment, the movement amount of the firstrotating shaft 53 a relative to the second rotating shaft 53 b) forrotating the sealing jaws 51.

One possible method for detecting the presence of articles trapped inthe sealed portion is a method of measuring the relative movement amountof one sealing jaw 51 in relation to the other sealing jaw 51. However,when the movement amount of sealing jaws 51 rotating in a circular orbitis measured, the configuration for measuring the movement amount islikely to be complicated. Here, because the relative movement amount ofthe first rotating shaft 53 a for rotating the sealing jaw 51 a relativeto the second rotating shaft 53 b for rotating the sealing jaw 51 b ismeasured, entrapment of articles in the sealed portion can be detectedwith a simpler configuration than it is detected by measuring themovement amount of the sealing jaws 51.

(4-4)

The bag making and packaging machine 3 according to the presentembodiment, is provided with the horizontal-direction pressing mechanism56 as a fluid-pressure-utilizing pressing mechanism. Thehorizontal-direction pressing mechanism 56 constantly presses the firstrotating shaft 53 a toward the second rotating shaft 53 b so that thetubular film Fc is to be pressed between the sealing jaws 51 when thetubular film Fc is sandwiched between the pair of sealing jaws 51.

Here, the entrapment of articles in the sealed portion can be detectedeven when the inexpensive horizontal-direction pressing mechanism 56,which does not itself perceive the force/moment or the like exerted onthe tubular film Fc, is used in order to apply pressure to the tubularfilm Fc between the sealing jaws 51.

(4-5)

In the bag making and packaging machine 3 according to the presentembodiment, the first rotating shaft 53 a support the sealing jaw 51 aat the first-end-part side (the right-end side) and the second-end-partside (the left-end side) in the longitudinal direction (the left-rightdirection) of the sealing surface 511 a with which the sealing jaw 51 asandwiches the tubular film Fc. The second rotating shaft 53 b supportsthe sealing jaw 51 b at the first-end-part side (the right-end side) andthe second-end-part side (the left-end side) in the longitudinaldirection (the left-right direction) of the sealing surface 511 b withwhich the sealing jaw 51 b sandwiches the tubular film Fc. One rotaryencoder 40 measures the first relative movement amount of the firstrotating shaft 53 a in relation to the second rotating shaft 53 b at thefirst-end-part side (the right-end side) (in the present embodiment, themovement amount of the right-side-end part of the first rotating shaft53 a relative to the second rotating shaft 53 b (the right-side movementamount)). The other rotary encoder 40 measures the second relativemovement amount of the first rotating shaft 53 a in relation to thesecond rotating shaft 53 b at the second-end-part side (the left-endside) (in the present embodiment, the movement amount of theleft-side-end part of the first rotating shaft 53 a relative to thesecond rotating shaft 53 b (the left-side movement amount)). Theentrapment determination part 30 a determines whether or not articlesare present in the sealed portion based on the right-side movementamount and the left-side movement amount.

Here, because the relative movement amounts (the right-side movementamount and the left-side movement amount) of the first rotating shaft 53a in relation to the second rotating shaft 53 b, in the left and rightend parts of the first rotating shaft 53 a, are used in thedetermination of the presence of trapped articles, it is easy toperceive that articles have been trapped regardless of the location inwhich they have been trapped in the sealed portion of the tubular filmFc.

For example, there could be a configuration with one rotary encoder 40,wherein only the movement amount of the right-side-end part of the firstrotating shaft 53 a relative to the second rotating shaft 53 b (theright-side movement amount) is measured. In this case, if articles gottrapped near the left-side-end part of the sealed portion of the tubularfilm Fc, the right-side-end part of the first rotating shaft 53 a wouldnot move by much relative to the second rotating shaft 53 b (i.e. thedifference in movement amount from that of a case when no articles aretrapped would not be notable). However, because both the left-sidemovement amount and the right-side movement amount are measured by tworotary encoders 40, it is easy to accurately determine that articleshave been trapped.

However, the configuration is not limited to this example, and only theleft-side movement amount or only the right-side movement amount may bemeasured by a rotary encoder 40. For example, in cases such as when itis unlikely a difference between the left-side movement amount and theright-side movement amount to be caused (e.g., when the longitudinalwidths of the sealing surfaces 511 a, 511 b are comparatively small),the entrapment of articles can be accurately determined even if only theleft-side movement amount or only the right-side movement amount ismeasured by a rotary encoder 40.

(4-6)

In the bag making and packaging machine 3 according to the presentembodiment, the entrapment determination part 30 a determines whether ornot articles are present in the sealed portion based on the statisticsof the relative movement amount (the movement amount of the firstrotating shaft 53 a relative to the second rotating shaft 53 b in thiscase) measured during a predetermined time period (the time periods X1,X2 in the present embodiment) by the rotary encoders 40. Particularly,the entrapment determination part 30 a in this case determines whetheror not articles are present in the sealed portion based on the averagevalue of the movement amount of the first rotating shaft 53 a relativeto the second rotating shaft 53 b, measured during the time periods X1,X2 by the rotary encoders 40.

Here, erroneous detection of the presence of articles is hardly caused,even if there is momentarily a comparatively large measurement error inthe relative movement amount of the first rotating shaft 53 a inrelation to the second rotating shaft 53 b, measured by the rotaryencoders 40.

(4-7)

In the bag making and packaging machine 3 according to the presentembodiment, the pair of sealing jaws 51 sandwich the tubular film Fcconveyed in the first direction (downward in this case) and laterallyseal the film along a direction (the left-right direction in this case)intersecting the first direction sequentially from the forward side inthe first direction, due to the sealing jaws 51 a, 51 b being rotatedalong a circular orbit. Within one sealing action by the sealing jaws51, the entrapment determination part 30 a determines whether or notarticles are present in the sealed portion in the time period X1 (anexample of the first time period), which begins at the point in timewhen the sealing action by the sealing jaws 51 a, 51 b is started andends at the point in time when cutting of the tubular film Fc by theknife 72 a arranged to the sealing jaw 51 b is started (an example ofthe first time point). Additionally, within one sealing action by thesealing jaws 51, the entrapment determination part 30 a determineswhether or not articles are present in the time period X2 (an example ofthe second time period), which begins at the point in time when cuttingof the tubular film Fc by the knife 72 a arranged to the sealing jaw 51b is finished (an example of the second time point), and ends at thepoint in time when the sealing action by the sealing jaws 51 a, 51 b isfinished.

In the bag making and packaging machine 3 using a rotating lateralsealing mechanism, the determination of the presence of trapped articlesis performed separately at the sealing action starting time and thesealing action finishing time, within one sealing action. Therefore,when bags are being packaged continuously, a determination of thepresence of articles of one-end side (the upper-end side during lateralsealing) of one bag B and a determination of the presence of articles ofthe other-end side (the lower-end side during lateral sealing) of thefollowing bag B can be performed separately. It is thereby easy to expelonly bags B in which presence of articles is actually caused asdefective products.

The configuration is not limited to this example, and the occurrence ofthe presence of articles trapped in the sealed portion may be determinedfor the entire sealing action. However, in order to expel only bags B inwhich the presence of trapped articles results in defective products, itis preferable to determine whether or not articles are present in thesealed portion separately in the time period X1 and the time period X2as described above.

(4-8)

In the bag making and packaging machine 3 according to the presentembodiment, the second rotating shaft 53 b is secured so as not to moveeither toward or away from the first rotating shaft 53 a. The firstrotating shaft 53 a is capable of moving toward or away from the secondrotating shaft 53 b. The rotary encoders 40 measure the movement amountof the first rotating shaft 53 a in the direction toward or away fromthe second rotating shaft 53 b as the relative movement amount when thefirst rotating shaft 53 a moves toward or away from the second rotatingshaft 53 b.

Here, because only the first rotating shaft 53 a can move toward or awayfrom the second rotating shaft 53 b and occurrence of presence ofarticles trapped in the sealed portion is determined by detecting themovement amount, the relative movement amount of the first rotatingshaft 53 a in relation to the second rotating shaft 53 b can be measuredwith a simple configuration to detect the presence of trapped articles.

(4-9)

Conventionally, alignment adjustment of the sealing jaws 51 is done byusing a thickness gauge. In the bag making and packaging machine 3according to the present embodiment, alignment adjustment of the sealingjaws 51 can be done based on the measurement result of the left-sidemovement amount and the right-side movement amount by the rotaryencoders 40. Therefore, it is possible to perform alignment adjustmentof the sealing jaws 51 with little variation in a short time.

(4-10)

By using the movement amount of the first rotating shaft 53 a relativeto the second rotating shaft 53 b measured by the rotary encoders 40, itis possible to detect dirt on the sealing jaws 51 as well as to detectwhether or not articles are present in the sealed portion.

When the sealing jaws 51 are dirty, the distance between the sealingsurface 511 a and the sealing surface 511 b decrease commensurately withrespect to the amount of dirt adhesion than when there is no dirt, andthe force with which the sealing jaw 51 b presses the sealing jaw 51 abecomes greater than when there is no dirt. As a result, the movementamount of the first rotating shaft 53 a relative to the second rotatingshaft 53 b in a case when the sealing jaws 51 are dirty becomes greaterthan in a case when the sealing jaws 51 are not dirty. Therefore, byperceiving the movement amount of the first rotating shaft 53 a relativeto the second rotating shaft 53 b and comparing this amount with, e.g.,the movement amount in cases of no dirt, dirt on the sealing jaws 51 canbe detected and instances of sealing strength being insufficient due todirt on the sealing jaws 51 can be prevented.

(5) Modifications

Modifications of the present embodiment are presented below. Themodifications may be combined as appropriate as long as they do notcontradict each other.

(5-1) Modification A

In the above embodiment, the bag making and packaging machine 3 utilizesthe rotary encoders 40 as movement amount detectors, but such anarrangement is not provided by way of limitation. Other movement amountdetectors may be attached to the ends of the second linking rods 83 andbe capable of measuring the amount of displacement of the second linkingrods 83. For example, load cells 41 may be attached to the ends of thesecond linking rods 83 as shown in FIG. 10, and the strength of theforce exerted on the load cells 41 may be used to measure the amount ofdisplacement of the second linking rods 83. Additionally, for example,potentiometers 42 may be attached to the ends of the second linking rods83 as shown in FIG. 11, and the change in resistance value may be usedto measure the amount of displacement of the second linking rods 83.

The results of inspection using real machinery indicates, among rotaryencoders, load cells, and potentiometers, that rotary encoders arecomparatively superior in terms of performance, and potentiometers arecomparatively superior in terms of cost.

(5-2) Modification B

In the above embodiment, the movement amount of the second linking rods83 is measured at the ends of the second linking rods 83, whereby themovement amount of the first rotating shaft 53 a relative to the secondrotating shaft 53 b is measured, but no limitation is provided thereby.The movement amount of the first rotating shaft 53 a relative to thesecond rotating shaft 53 b may be measured by arranging the rotaryencoders 40 or other movement amount detectors to portions of the secondlinking rods 83 where they are attachable other than the ends, andmeasuring the movement amount of the second linking rods 83 at thosepositions. The movement amount of the first rotating shaft 53 a relativeto the second rotating shaft 53 b may be measured by directly measuringthe movement amount of the first rotating shaft 53 a itself rather thanmeasuring the movement amount of the second linking rods 83.

(5-3) Modification C

In the above embodiment, the presence of trapped articles during lateralsealing is determined in the bag making and packaging machine 3 using arotating lateral sealing mechanism, but no limitation is providedthereby.

For example, the entrapment of articles may be determined with aconfiguration similar to that of the above embodiment, in a packagingmachine using a lateral sealing mechanism in which a sealing jaw 151 ais revolvably driven in a D-shaped path in a side view by a firstrevolving shaft 153 a as an example of the first support part, and asealing jaw 151 b is revolvably driven in a D-shaped path in a side viewby a second revolving shaft 153 b as an example of the second supportpart, whereby the tubular film Fc is sandwiched and laterally sealedbetween the pair of sealing jaws 151, as shown in FIG. 12.

In this case, the first revolving shaft 153 a and the second revolvingshaft 153 b are revolvably driven in a D-shaped path in a side view, bymoving the first revolving shaft 153 a and the second revolving shaft153 b toward or away from each other while rotating (refer to the arrowsA3 in FIG. 12). In other words, the first revolving shaft 153 a and thesecond revolving shaft 153 b are both capable of moving toward or awayfrom the other. Therefore, the movement amount detectors in this caseare configured so as to measure the movement amounts of both revolvingshafts 153 a, 153 b by using rotary encoders or the like, and tocalculate the relative movement amount of the first revolving shaft 153a in relation to the second revolving shaft 153 b.

For example, in a packaging machine in which at least one of two sealingjaws is driven linearly toward the other and sandwich a film between thesealing jaws, the presence of trapped articles may be determined with aconfiguration similar to that of the above embodiment. In a case whenone sealing jaw is driven so as to move toward or away from the other, amember supporting the one sealing jaw so that the sealing jaw islinearly driven, and a member supporting the other sealing jaw so thatthe other sealing jaw does not move, would be examples of the firstsupport part and the second support part, respectively. In a case whenboth sealing jaws are driven so as to move toward or away from eachother, members supporting the sealing jaws so that the sealing jaws arelinearly driven would be examples of the first support part and thesecond support part.

(5-4) Modification D

In the lateral sealing mechanism 17 according to the above embodiment,the sealing jaw 51 a and the sealing jaw 52 a are provided to the firstrotating body 50 a, the sealing jaw 51 b and the sealing jaw 52 b areprovided to the second rotating body 50 b, and the sealing jaw 51 a andthe sealing jaw 51 b alternate with the sealing jaw 52 a and the sealingjaw 52 b to sandwich and laterally seal the tubular film Fc, but theinvention is not limited to this configuration.

For example, in the bag making and packaging machine 3, the sealing jaw51 a alone may be provided to the first rotating body 50 a, the sealingjaw 51 b alone may be provided to the second rotating body 50 b, andlateral sealing may be performed using the sealing jaws 51 alone.Additionally, for example, the bag making and packaging machine 3 mayhave three or more groups of sealing jaws, and lateral sealing of thetubular film Fc may be performed using these groups of sealing jawsalternately.

(5-5) Modification E

The entrapment determination part 30 a according to the above embodimentdetermines whether or not articles are present in the sealed portion bycalculating the average value of the movement amount of the firstrotating shaft 53 a relative to the second rotating shaft 53 b measuredduring the time periods X1, X2, and comparing the average value with themaximum value Dmax of the movement amount of the first rotating shaft 53a relative to the second rotating shaft 53 b in a case when no articlesare present, but no limitation is provided thereby. For example, theentrapment determination part 30 a may determine that articles arepresent in the sealed portion when the movement amount of the firstrotating shaft 53 a relative to the second rotating shaft 53 b measuredduring the time periods X1, X2, includes an element that surpasses themaximum value Dmax. In this case, the entrapment determination part 30 acan quickly determine whether or not articles are present in the sealedportion.

The entrapment determination part 30 a may also determine whether or notarticles are present in the sealed portion by calculating anintermediate value or another statistical value of the movement amountof the first rotating shaft 53 a relative to the second rotating shaft53 b measured during the time periods X1, X2, and comparing thisstatistical value with the maximum value Dmax of the movement amount ofthe first rotating shaft 53 a relative to the second rotating shaft 53 bin a case when no articles are present.

The entrapment determination part 30 a may also recognize the differencein the shapes of the graphs of the movement amount of the first rotatingshaft 53 a relative to the second rotating shaft 53 b caused by theoccurrence of the presence of trapped articles (see FIGS. 9(a) and9(b)), and thereby determine whether or not articles are present in thesealed portion.

(5-6) Modification F

In the above embodiment, the bag B is cut away from the tubular film Fcby the knife 72 a arranged to the sealing jaw 51 b or 52 b andconfigured to protrude toward the sealing jaw 51 a or 52 a, but nolimitation is provided thereby.

For example, a knife accommodated in a space formed in one sealing jaw51 of a pair of sealing jaws 51 may be driven so as to move toward theother sealing jaw 51, and the bag B may thereby be cut away from thetubular film Fc. In this case as well, the occurrence of the entrapmentof articles in the sealed portion can be determined based on themovement amount of the first rotating shaft 53 a relative to the secondrotating shaft 53 b in a case when no articles are present in the sealedportion, and the movement amount of the first rotating shaft 53 arelative to the second rotating shaft 53 b measured by the rotaryencoders 40 during the sealing action by the sealing jaws 51.

Another possible option is to not provide a knife 72 a to the sealingjaw 51 b or 52 b, and to have the sealing jaws 51, 52 perform lateralsealing only (the bag B would not be cut).

(5-7) Modification G

In the above embodiment, the bag making and packaging machine 3 isdescribed as an example of the packaging machine according to thepresent invention, but the packaging machine according to the presentinvention is not limited as such. For example, the packaging machine maybe designed so that it only includes the lateral sealing mechanism 17portion of the bag making and packaging machine 3.

INDUSTRIAL APPLICABILITY

In the packaging machine according to the present invention, sealingmembers sandwich and seal a packaging material. The packaging machine isuseful for being capable of detecting when articles are present in asealed portion even when the mechanism used as the drive source of thesealing members is incapable of perceiving the force/moment exerted onthe packaging material by the drive source and positional informationpertaining to the drive source, directly from information obtained fromthe drive source.

REFERENCE SIGNS LIST

-   3 Bag making and packaging machine (packaging machine)-   30 a Entrapment determination part-   40 Rotary encoder (movement amount detector)-   41 Load cell (movement amount detector)-   42 Potentiometer (movement amount detector)-   51 (51 a, 51 b) Sealing jaw-   52 (52 a, 52 b) Sealing jaw-   151 (151 a, 151 b) Sealing jaw-   53 a First rotating shaft (first support part)-   53 b Second rotating shaft (second support part)-   153 a First revolving shaft (first support part)-   153 b Second revolving shaft (second support part)-   56 Horizontal-direction pressing mechanism (fluid-pressure-utilizing    pressing

1. A packaging machine in which a pair of sealing members is configuredto sandwich and seal a sealed portion of a film, the packaging machinecomprising: a first support part configured to support one of thesealing members; a second support part configured to support the otherof the sealing members; a movement amount detector configured to measurethe relative movement amount of the first support part in relation tothe second support part in an approaching direction or a moving awaydirection, when the first support part and the second support partapproach or move away; and an entrapment determination part configuredto determine whether or not articles are present in the sealed portionbased on the relative movement amount.
 2. The packaging machineaccording to claim 1, wherein the pair of sealing members are configuredto be rotated in a circular orbit, whereby the sealing members sandwichand laterally seal the film along a direction intersecting a firstdirection, the film being conveyed in the first direction and formedinto a tubular shape.
 3. The packaging machine according to claim 2,wherein the first and second support parts are rotating shafts forrotating the sealing members.
 4. The packaging machine according toclaim 2, further comprising: a fluid-pressure-utilizing pressingmechanism configured to constantly press the first support part towardthe second support part so that the film is to be pressed between thesealing members when the film is sandwiched between the pair of sealingmembers.
 5. The packaging machine according to claim 1, wherein each ofthe first and second support parts is configured to support the sealingmember at a first-end side and a second-end side in the longitudinaldirection of a surface with which the sealing members sandwich the film;the movement amount detector is configured to measure, as the relativemovement amount, a first relative movement amount of the first supportpart in relation to the second support part at the first-end side, and asecond relative movement amount of the first support part in relation tothe second support part at the second-end side; and the entrapmentdetermination part is configured to determine whether or not articlesare present in the sealed portion based on the first relative movementamount and the second relative movement amount.
 6. The packaging machineaccording to claim 1, wherein the entrapment determination part isconfigured to determine whether or not articles are present in thesealed portion based on statistics of the relative movement amountmeasured during a predetermined time period by the movement amountdetector.
 7. The packaging machine according to claim 6, wherein theentrapment determination part is configured to determine whether or notarticles are present in the sealed portion based on an average value ofthe relative movement amount measured during the predetermined timeperiod by the movement amount detector.
 8. The packaging machineaccording to claim 1, wherein the pair of sealing members are configuredto be rotated in a circular orbit, whereby the sealing members sandwichand laterally seal the film along a direction intersecting a firstdirection sequentially from the forward side in the first direction, thefilm being conveyed in the first direction and formed into a tubularshape; and the entrapment determination part is configured to determinewhether or not articles are present in the sealed portion, both in afirst time period beginning at a start of a sealing action by thesealing members and ending at a first time point and in a second timeperiod beginning at a second time point after the first time point andending at a finish of the sealing action, within the single sealingaction.
 9. The packaging machine according to claim 1, wherein thesecond support part is secured so as not to move in a direction towardor away from the first support part; the first support part is capableof moving in a direction toward or away from the second support part;and the movement amount detector is configured to measure the movementamount of the first support part in the direction toward or away fromthe second support part as the relative movement amount when the firstsupport part moves toward or away from the second support part.